Well control equipment



3 Sheets-Sheet 1 Filed April 6. 1956 A erbe/f /4//ex7 INVENTOR. an

March 17, 1959 H. ALLEN WELL CONTROL EQUIPMENT 3 Sheets-Sheet 2 Filed April 6, 1956 IN VEN TOR.

A TTO/P/VEVJ March 17, 1959 H. ALLEN WELL Filed April 6, 1956 CONTROL EQUIPMENT 3 Sheets-Sheet 3 fler er 2 /4//e/7 INVENTOR.

A TTOR/VE VJ United States Fatent WELL CONTROL EQUIPMENT Herbert Allen, Houston, Tex, assignor to fiameron Iron Works, Inc., Houston, Tex., a corporation of Texas Application April 6, 1956, Serial No. 576,629

3 Claims. (Cl. 251-1) This invention relates to control equipment adapted to be made up as a part of a wellhead to provide positive control of the Well, and more particularly to control equipment which will not interefere with normal drilling operations, but may be instantly activated when dangerous well conditions occur and which will permit continued drilling with the well bore closed at the surface.

It is considered to be good drilling practice, especially where high well pressures are expected to be encountered, to employ a bank of three blowout preventers to control the well. The blowout preventers are arranged in tandem with the intermediate preventer employing blanking rams which will seal the blowout preventer bore when empty. The function of the intermediate preventer may be accomplished by a master valve. The upper and lower blowout preventers employ drill pipe rams which will seal about the cylindrical drill pipe portion of a drill string. The two drill pipe rams provide, in elfect, a pressure compartment which may function in the manner of a pressure lock to insert or withdraw the drill string from the well while maintaining complete pressure control.

The above arrangement will not in itself permit drilling under pressure and where it is desired to be able to drill under pressure, a fourth pressure seal must be provided which will provide a seal with the non-circular kelly. Several Kelly seals are available. One form is a device which is permanently secured to the wellhead and provided with a stripper seal through which the kelly and drill pipe may be run and withdrawn. The stripper seal rotates with the kelly. A rotating seal is provided between relatively rotatable parts of the device. This form of device is constantly subject to wear when it is in position, whether being used or not. Another form of such equipment employs a stripper seal which may he landed in an uppermost blowout preventer of a particular design, and provide with the uppermost blowout preventer the rotating seal desired. This form of Kelly seal may be left in position continuously, and when so used, is subject to the objection of constant wear. When it is desired to use this type of Kelly seal, it is necessary to pull the drill string and remove the rotary master bushing before the Kelly seal can be landed in the blow out preventer.

In each of the forms of Kelly seal referred to above, the height of the wellhead equipment, and hence, the

necessary height of the derrick floor is substantially increased. To be immediately available, each form of presently available Kelly packer must be installed so as to be subject to continuous wear even though not being used to contain the well. It is diflicult and inconvenient to strip drill pipe through the stripper seal. As the stripper seals are continuously distorted in normal drilling operations an operator can never be quite sure that the packers have not been torn or darnaged so that they will not hold pressure when they are suddenly needed.

It is an object of this invention to provide wellhead equipment for drilling with the well bore closed at the surface which is made up as a part of the wellhead and is always ready for immediate use, but which is not subject to wear except while being used to drill with the well bore closed.

Another object is to provide a rotatable means for sealing about a kelly which is always in position and ready for immediate use and which does not interfere with normal drilling operations.

Another object is to provide a means for sealing about a kelly which does not substantially increase the overall height of the wellhead.

Another object is to provide a power-operated blowout preventer for sealing about a kelly which rotates with the kelly when being used.

Another object is to provide a rotatable blowout preventer in which the lateral or horizontal dimensions of the apparatus are held to a minimum to minimize inertia problems.

Another object is to provide with a single blowout preventer means for sealing an open hole, for sealing about a section of tubing of a drill string or the kelly of a drill string, and for drilling with the well under positive and complete control.

Another object is to provide for complete control of a well with a battery of two blowout preventers which will form a seal with a kelly for drilling under pressure, which will close off the open hole when the drill string is entirely removed, and which will strip the drill string into and out of the well under pressure.

Another object is to provide a rotating blowout preventer with a single hand or power operator for four rams.

Other objects, features and advantages of this inven tion will be apparent from a consideration of the specification, the drawings and the appended claims.

In the drawings wherein there is shown by way of illustration several forms of the invention and wherein like reference numerals indicate like parts:

Fig. l is a view in elevation of a wellhead including the control means of this invention with portions of the wellhead shown in section for purposes of illustration;

Fig. 2 is a fragmentary view on an enlarged scale taken along the line 2-2 of Pig. 1 illustrating a universal type of blowout preventer preferably used with this invention;

Fig. 3 is a fragmentary view on an enlarged scale taken along the lines 3-4! of Fig. 1 further illustrating the preferred blowout preventer rams;

Fig. 4 is a view partly in elevation and partly in cross- I section illustratin a fiuid operated form of this invention;

Fig. 5 is a fragmentary view in horizontal cross-section illustrating the manner in which the several rams seal about the kelly and to the transverse bores of the blowout preventer of Fig. 4; V

Fig. 6 is a view partly in elevation and partly in crosssection illustrating a manually operated form of this in vention; and

Fig. 7 is a view partly in elevation and partly in section illustrating and electrically operated form of this invention.

Referring to Fig. 1, there is shown a typical application of this invention to a wellhead. A casing head 10 is secured to surface casing 11. It will be understood that as the well deepens, the casing head 10 may have additional sections added thereto from which several strings of easing may be suspended in the well. A blowout preventer indicated generally at 12 is rigidly secured to the casing head 10 and is of conventional construction except that it preferably employs a novel type of ram which will seal about either a kelly, a length of tubing, or will seal the blowout preventer bore. A second blowout preventer indicated generally at 13 is spaced above and secured to the lowermost blowout pre venter by a spool 14. The blowout preventer 13 is so constructed that it will rotate with the drill string when its rams are in engagement with the drill string and permitdrilling while the well is held under pressure by the rams of this blowout preventer. These rams are again preferably of the universal type. The kelly 15 which forms the upper end of the drill string and extends through both blowout preventers is driven from the derrick platform 16 by a conventional rotary table indicated generally. at 17.

' The above pressure control system gives complete control of the well at all times as wellas permitting drilling under pressure while utilizing only two blowout preventers. The universal type of rams permit the drill string to be stripped out of the hole while pressure control is maintained. By way of example the kelly 15 can be raised until the first joint of the drill string is above the lower blowout preventer 12. The rams of the lower blowout preventer 12 may then be closed and pressure within the chambers between the two blowout preventers bled off through fitting 18. The rams of the upper blowout preventer can then be opened and the string raised. The first section of tubing may be supported in the turntable and the kelly removed. This operation may be repeated and the several sections of the string of tubing broken out. After the bit has been stripped through the lower blowout preventer, the lowermost blowout preventer is closed and the universal type rams seal the bore in the blowout preventer to act as a master valve and close in the well.

If while drilling the density of the returns begin to decrease and the mud weight reduces to a value which the operator fears is not sufiicient to contain the well, the rotary table may be stopped and the rams of the upper rotatable preventer advanced to engage and seal with the kelly. Rotation may then be resumed and the mud return line choked so that the mud pumps will build up a pressure within the well to compensate for the reduced weight of the drilling fluid. This condition may be maintained and additional sections of tubing added through the two blowout preventers in the customary manner to permit continued drilling under pressure. Meanwhile steps can be taken to add weight to the mud or correct the formation condition which is causing loss of mud weight. Drilling under pressure with the top blowout preventer containing the well may continue for hours or days as is necessary to correct the condition which is causing loss of mud weight.

' There are certain conditions under which it is desirable to drill with the well under pressure and this system may also be utilized for such service as the two blowout preventers permit the stripping in and out of the drill string and continued making of hole while the well is under pressure.

It will be appreciated that the uppermost rotatable blowout preventer 13 may be added to a conventional bank of blowout preventers and will serve as a Kelly packer to permit drilling under pressure. When this sort of system is used, the conventional bank of blowout preventers is used for stripping the drill string into and out of the well and the rotatable blowout preventer utilized for drilling under pressure.

Referring now to Fig. 4, the rotatable blowout preventer 20 employs four rams which are contoured to fit a square kelly. The unit includes a base 19 which may be rigidly secured to the spool 14. The base 19 has a central bore 21 which forms a continuation of the well bore and is adapted to pass the drill string and other tools into the well.

Rotation of the body 22 of the blowout preventer about the axis of bore 21 is provided by a tubular extension 23 depending from body 22 and telescoped over the upper portion of base 19. The body is supported on the base for rotation relative to the base by suitable ball and roller bearing assemblies indicated generally at 24 and 25. The anti-friction rollers and balls may be provided in any desired manner which will hold the body 22 and base 19 in the desired telescoped relationship and permit relative rotation between the body and base. For instance, the ball bearing assembly may be provided by confronting races in the body and base and the balls fed into the races through radial holes, plugged as at 30.

A rotating seal between the base 19 and body 22 is provided to seal between these two parts while the body of the blowout preventer is rotating. This seal may be conveniently provided by forming an annular recess 26 in the upper outer periphery of base 19 and packing the annular groove so provided with V packing 27.

To seal about a square kelly, the body 22 is provided with four rams indicated generally at 28 which reciprocate in lateral or horizontally extending bores 29. The bores 29 are spaced equally about and extend radially from the bore 31.

The several rams when extended into engagement with kelly 15 form a seal with the kelly, with each other and with the body of the blowout preventer to seal in the well. The coaction of these several elements can best be seen in Fig. 5. Each of the rams 28 has a square or blunt nose 32 having a horizontal dimension substantially equal to a side of the square kelly. The ram tapers from this point to the full width of the ram at approximately the intersection of the ram bores 29 with the rams extended. This tapered wall or side 33 is formed on approximately a 45 angle. The seal element 34 of each ram extends back from the ram front to the mid section of the ram and upwardly into engagement with the roof of ram bore 29. As is customary, the seal elements 34 also extend to the sides of the ram about its upper half and engage the side walls of the ram. The seal material is also exposed in the face of tapered walls 33 of the rams so that the seal material of adjacent rams will be in abutment and seal between adjacent rams. As best shown in Fig. 4, this ram construction is provided by a base 35 to which the flexible portion 34 of the ram is secured and held by a floating retainer 35a. Retainer 35a is secured to ram base 35 by a bolt 37 which will permit relative movement between the retainer 35a and ram base 35 along the axis of the lateral bore 29. This construction will permit the retainer 35a to abut or be in close proximity with the kelly to provide a dam for the sealing material without limiting movement of the ram.

This preventer has four rams. It is desirable to operate the several rams from a single motor to simplify the structure and reduce inertia problems. This may be accomplished by providing a single large fluid motor operably connected to each of the rams. Such a fluid motor is provided by the annular pressure responsive member or piston 36 mounted for vertical reciprocation within pressure chamber 37. Pressure chamber 37 surrounds the bore through the blowout preventer and is provided by a bell housing indicated generally at 39 which fits over a reduced diameter tubular extension 40 on the top of the blowout preventer. The bell housing is scaled to the body of the blowout preventer by an O-ring 41 carried in a groove in the upper extremity of the reduced diameter section 40 and by an O-ring 60 at the outer lip of the bell. A groove for the O-ring 60 is provided by the body 22 and a retainer 42 which is welded to the body. The O-ring retainer 42 is generally angular in crosssection having one leg extending horizontally and one vertically. The vertical leg is welded to the body 22 and the free end of the horizontal leg has a sliding fit with the lip of the bell housing 39.

This piston 36 is annular in configuration and has a central bore dimensioned to receive the upstanding tubular member 40. An D ring 43 is carried by the piston and forms a seal with the tubular member 40. A second O-ring 44 carried at the outer periphery of the pisto forms a seal with the bell housing 39.

A suitable force transmitting means is provided between the pressure responsive member 36 and each of rams 28. Preferably, the forc transmitting means is provided by double racks and pinions for each ram to translate the vertical movement of the piston into horizontal movement of the rams. For this purpose, pinion shafts 45 are journaled for rotation in housing 22 and carry an exterior pinion 46 engageable with a rack 47 carried by piston 36 and an interior pinion 48 engageable with a rack 49 which drives a ram. The drive between rack 49 and the ram is provided by a key 50 which locks the rack 49 and the ram body 35 so that they will reciprocate with each other. To simplify the structure it is preferred that a single rack 47 drive the pinions of two rams and for this purpose the pinion shafts 45 of two adjacent rams are so disposed as to engage their exterior pinions 46 with toothed sections 47a and 47b of rack 47 as shown on the left hand side of Fig. 4.

In addition to the advantage of simplifying the structure and simplifying inertia problems, this form of force a transmitting means does not employ a shaft which must be forced into the blowout preventer under pressure. The transmission of force between the exterior and interior of body 22 is through a rotating shaft 45 instead of a reciprocating shaft as is commonly employed. Thus, the motor does not have to overcome the pressure of the well acting over the area of the several shafts.

Power may be applied to the motor 36 through a swivel ring indicated generally at 51. This ring is carried by base 19 and has an inner annular surface 52 which fits closely about a complementary surface 53 on the depending portion 23 of body 22 and rotates relative thereto. Surface 52 has three spaced annular grooves therein and O-rings 54, 55 and 56 are positioned in these grooves to form a sliding seal between surfaces 52 and 53. The ring 51 has an annular groove 57 opening into surface 52 between Q-rings 54 and 55. Likewise, a groove 58 is provided which opens into surface 52 between O-rings 55 and 56. The O-rings 54, 55 and 56 and the surface 53 of body 22 cooperate to confine fluid within the grooves 57 and 58. A fluid inlet 59 is provided into groove 57 and similar inlet 61 provides entrance into groove 58. Suitable piping indicated diagrammatically at 62 and 63 interconnect the inlets 59 and 61 to a four-way valve 64 which is in turn connected to a pump 65. Preferably pump 65 delivers air to piston 36, but if desired, the operating fluid may be a liquid. If a liquid is used, a reservoir may be provided to collect liquid from chamber 37 and supply it to pump 65 in the usual manner. This system will alternately pressurize one of grooves 57 and 58 and relieve the pressure from the other groove by the expedient of reversing the four-way valve 64.

Fluid from the grooves 57 and 58 is supplied to the two sides of the pressure responsive member 36 to reciprocate the rams 28. A passageway 67 communicates with surface 53 between O-rings 54 and 55 and a conduit 68 connects passageway 67 to the chamber 37 below the piston 36. A like passageway 69 connects surface 53 between O-rings 55 and 56 to the top side of piston 36 through a conduit 70.

The operation of the Fig. 4 form of blowout preventer will now be explained. It will be assumed that it is secured to the top of a bank of blowout preventers of conventional form and the rams 28 are retracted. Now let it be supposed that a condition suddenly arises which renders it improvident to continue drilling in an open hole and it is desired to maintain a pressure on the hole. The rotary table will be stopped and four-way valve 64 turned to provide pressure to the top of piston 36 and to remove pressure from the bottom of piston 36, this being the position shown in Fig. 4. The pressure supplied by pump 65 will begin moving piston 36 downwardly which will cause rams 28 to begin moving inwardly toward kelly 15. If the flats of the kelly are not parallel with the blunt noses of the rams, the engagement between .the kelly and rams will act as a couple to rotate the blowout preventer to position the Kelly flats parallel to the blunt faces of the rams-the position shown in Fig. 5. At this time the well will be under complete control and the operator may resume drilling while holding the rams under pressure with pump 65. The body 22 which carries the rams 28 will rotate about base 19 and the V packing 27 will provide a rotating seal between the body and base to contain well pressure. Drilling may be continued in this manner until the condition which made it deisrable to drill under pressure has been corrected.

Referring again to Fig. 1 and Fig. 2, it will be noted that the principal difference between blowout preventer 13 of Fig. 1 and blowout preventer 20 of Fig. 4 lies in the type of ram utilized. In Fig. 1 only two rams are utilized. The rams of Figs. 1 and 2 are designed to seal an open hole or to seal about a kelly or a tubing. Any rams which will seal an open hole, seal about a kelly or about a tubing, as will ram 71, will be referred to in this application as a universal type of ram. Rams 71 are made up of a plurality of thin ram segments 72 arranged side-by-side in ram bore 73 and mounted on a carrier 74. The under surface of carrier 74 is provided with a rack 75 which meshes with pinion 76. Pinion 76 is driven in the same manner as corresponding pinion 48 of the Fig. 4 form of blowout preventer. Each ram segment 72 includes a metal base 77 and carries on its forward section packing 78. The body 77 at its front end is formed in the general configuration of an I-beam with the web terminating short of the flanges as best seen in Fig. 3. Packing 78 is carried between the upper and lower cross-heads at the I-beam. The body 77 is notched at its top at a point spaced from the forward edge of the ram segment and the packing material 78 fills this notch as at 79. The width dimension of the ram segments is such that the ram segments slide relative to each other within bore 73. When the packing 78 is stressed by being forced into engagement with an opposite ram, a kelly or tubing, the packing of each ram segment will engage the packing of an adjacent ram segment and the roof of ram bore 73. The end ram segments will engage the side wall of ram bore 73. In this manner, the several ram segments will cooperate to seal the blowout preventer bore.

The ram segments are moved into and out of the blowout preventer bore by a unique compensator arrangement which permits them to assume the desired contour to seal the open blowout preventer bore or about different shaped objects in the blowout preventer bore. Referring to Fig. 1, it will be noted that the body 77 of each ram segment is notched as at 80. A pusher 81 on carrier 74 extends the width of the carrier and is received in notches to cause reciprocation of the ram segments upon movement of carrier 74. A flexible bag 82 of smooth wall granular elements 83, preferably cylindrical balls, extends through notch 80 in front of pusher 81 and from side wall to side wall of ram bore 73. A similar bag 84 of granular elements 85 is positioned to the rear of pusher 81. As pusher 81 e xerts force on the ram segments to move them toward the center of the blowout preventer bore, balls 83 and 85 will flow in hydraulic manner to equalize the force on the several ram segments 72. Thus, as a resistance to movement is encountered in the blowout preventer bore, the front of the ram segments will assume the contour of the portion of the drill string within the bore of the blowout preventer.

It is desirable to design the throw of each ram for minimum possible movement and for this purpose, the front of each ram 71 should assume the general contour of the blowout preventer bore when the ram is retracted. For this purpose, a backstop 86 having the general contour of the blowout preventer bore may be provided to contact the rear of each ram segment as the ram is retracted to cause the ram front to assume the general contour of the blowout preventer bore. For further illustration and description of the rams shown in Figs. 1 and 2, see my co-pending application filed on even date herewith, Serial No. 576,696, filed April 6, 1956, and entitled, Blowout Preventer and Ram Therefor."

It will be noted that the lower blowout preventer of Fig. l is also equipped with universal type rams and when both blowout preventers 12 and 13 are so equipped, only two blowout preventers are required to provide absolute control of well pressure at all times and to permit drilling under pressure as heretofore explained.

Referring now to Fig. 6, there is illustrated a rotatable blowout preventer constructed in accordance with this invention which is manually operable. The blowout preventer body 22a is mounted for rotation about a central bore through base 190 with anti-friction bearings 25a between the body and base. The rotating seal between the body and the base is provided by V packing 27a. Four rams 28 are reciprocal in ram bores 29a in the manner of the Fig. 4 form of blowout preventer with the ram driven by pinion 48 and rack 49. The drive pinions 48 are rotated by an exterior rack and pinion 47c and 46 respectively. The racks 470 are mounted for vertical reciprocation in guides 90 and carriedby a crosshead indicated generally at 89. The crosshead 89 includes an inner ring 91 and an outer ring 92 which rotate relative to each other. A ball race 93 is disposed between the two rings 91 and 92 and forces the inner ring to reciprocate vertically with the outer ring.

The crosshead 89 is reciprocated by a simple handoperated device which is carried by base 19a. This hand operator includes a plurality of vertical screws 94 which are threadedly received in outer ring 92 and which are journaled for rotation in journal boxes 95. The journal boxes 95 are secured to base 19a to hold the screws 94 against reciprocation. Each screw 94 carries a pinion 96 and a ring wheel 97 extends circumferentially about all of the screws 94. Wheel 97 has a spur gear 98 on its inner periphery which meshes with pinions 96. Rotation of the ring wheel 97 will rotate screws 94 and reciprocate crosshead 89 which will in turn drive the rams in or out depending upon the direction of rotation. The threaded connection between crosshead 89 and screws 94 is self locking and holds the rams in position until wheel 97 is rotated.

Referring now to Fig. 7, there is shown a rotatable blowout preventer in which the rams are reciprocated by electric motors. The blowout preventer body 22b is mounted for rotation about a base 19b with bearings 25b providing for relative rotation between the body and base while preventing relative longitudinal movement of these elements. A rotating seal 27b confines fluid to the interior of the blowout preventer while permitting rotation of the body. A pair of rams 35b employing ram packing 34b with a V-shaped notch in the ram front may be employed or the universal type of ram may be employed.

Reciprocation of the rams may be provided by a rod 101 which has a square head 102 received within a square slot 103 in the rear of the ram. Slot 103 extends to the bottom of the ram to permit the ram to be moved downwardly over the head 102 of the rod and overhanging flange members 104 prevent withdrawal of the head 102 from the ram during reciprocation of the rod by electric motor 105. The arbor 106 of the electric motor drives a worm wheel 107 which is mounted for rotation in ball races 108 and 109. Wheel 107 is provided with a threaded bore which engages threads 110 of rod 101 and upon rotation of wheel 107 cause reciprocation of rod 101. The motor 105 may be provided with suitable limit stops as by overload switches to protect the motor. The gear train between the ram and motor is of the self-locking type and ram 35b is movable only by rotation of arbor 106.

' Electric current is fed to motor 105 through leads 111 and spectively of a slip ring indicated generally at 115. Current is fed to the slip ring through lines 116 and 117 which are connected to contact rings 118 and 119 respectively of the slip ring. These contact rings 118 and 119 are carried in a suitable housing 120, preferably explosion proof, which is mounted for rotation about body 22b.

Suitable reversing switch means, now shown, is utilized to reverse flow of a D. C. current through wires 116 and 117 to operate motor 105. By employing a D. C. motor the direction of rotation of arbor 106 may be easily controlled by controlling the incoming signal.

From the above, it will be seen that all of the objects of this invention have been attained. There has been provided a rotatable blowout preventer which is always in position for immediate use and yet does not interfere with normal drilling operations. The preventer permits drilling under pressure. This blowout preventer has been combined with a universal type of ram so that only two blowout preventers need be used to give full control of a well and to permit drilling under pressure. The rotatable blowout preventer may be operated manually or by a fluid or electric motor as desired. The rotating seal is long lasting because it is not subject to wear except when the blowout preventer is actually being used to drill under pressure.

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the apparatus.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

-As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed 1. Well control equipment comprising, a base adapted to be secured to a casing head, a central bore through the base for passing a drill string, a blowout preventer having a plurality of circumferentially arranged sealing rams movable toward and away from the central axis of said bore, means mounted for reciprocating in a direction parallel to the axis of the bore through the base and connected to the rams to move them toward and away from the central axis of said bore, means for reciprocating said first named means, means mounting the blowout preventer on the base for relative rotation therewith about the axis of the bore through the base, and means providing a rotating seal between the base and blowout preventer.

2. Well control equipment comprising, a base adapted to be secured to a casing head, a central bore through the base for passing a drill string, a blowout preventer having a plurality of circumferentially arranged sealing rams movable toward and away from the central axis of said bore, means mounted for reciprocating in a direction parallel to the axis of the bore through the base and connected to the rams to move them toward and away from the central axis of said bore, a single wheel for operating the reciprocating means and simultaneously moving the rams toward and away from the central axis of said bore, means mounting the blowout preventer on the base for relative rotation therewith about the axis of the bore through the base, and means providing a rotating seal between the base and blowout preventer.

3. Well control equipment comprising, a base adapted to be secured to a casing head, a central bore through 112 connected to contact rings 113 and 114 rethe base for passing a drill string, a blowout preventer 10 having a plurality of circumferentially arranged sealing References Cited in the file of this patent rams movable toward and away from the central axis of said bore, a single pressure responsive means mounted UNITED STATES PATENTS for movement in a direction parallel to the axis of the R 20,631 MacClatchie Jan. 18, 1938 bore through the base, force transmitting means between 5 1 5 0 7 3 Collins N 10, 1925 the pressure responsive means and the rams for recip- 11586923 Townsend Ju e 1 1925 rocating the rams, means mounting the blowout preventer 2,192,805 Seamark Mar 5 94 on the base for relative rotation therewith about the 2,194,258 Allen Mar. 19, 1940 axis of the bore through the base, and means providing 2 243 340 HH d May 27 1941 a rotating seal between the base and blowout preventer. 10 

